1. Field of the Invention
The present invention relates to an antireflection laminate, a polarizing plate and an image display device.
2. Description of the Related Art
In various image display devices such as liquid crystal display device (LCD), plasma display panel (PDP), electroluminescent display (ELD), cathode ray tube display device (CRT), field emission display (FED) and surface-conduction electron-emitter display (SED), an antireflection laminate (antireflection film) is disposed on the display surface so as to prevent the reduction in contrast due to reflection of outside light or external image. Also, a light-diffusing sheet is used on the backlight side of a liquid crystal display device. The antireflection film is used on the outermost surface of a display and therefore, required to satisfy various film strengths, for example, scratch resistance against fine scratches and film hardness high enough to endure the pressure on writing with a writing tool.
In recent years, with the expansion of display market as represented by LCD, PDP and the like and the growing in display size, the antiglare laminate disposed on the outermost surface of a display is also required to be improved in the antiglare and other properties. In particular, there are demanded, for example, 1) an improvement of contrast, 2) an enhancement of sharpness of transmitted image, 3) a reduction in character blurring and 4) an enhancement of pitch-black looking (dense black appearance) when the display is displayed in black.
Also, the growing in size of the display involves a requirement to increase the size of the antiglare laminate itself used as a surface element of the display, but in some cases, the visibility as a display body is somewhat decreased due to a physical change (e.g., unevenness) of the antiglare laminate caused by the increase in size.
The visibility reduction due to the increase in size of the antiglare laminate can be overcome by enhancing the antiglare performance of the antiglare laminate, but it is difficult to satisfy the requirement for improvements 1) to 4) above. That is, the enhancement of antiglare property is generally considered to be in a contradictory relationship with the requirement for improvements 1) to 4) above. An antiglare laminate satisfying both of these contradictory requirements is demanded to be developed.
For satisfying all of the improvements 1) to 4) above, there is proposed a method where fine particles are aggregated by fives or more in a layer having hardcoat property to create a desired irregularity shape on the outermost surface of the layer having hardcoat property and a surface adjusting layer is formed for adjusting the irregular surface of the layer having hardcoat property and where the fine irregularities present along the irregularity shape can be filled and smoothed by the surface adjusting layer on a scale of 1/10 or less of the irregularity scale (peak height and peak-to-peak distance of irregularities) in the surface roughness forming the irregularity shape to form smooth irregularities and thereby the peak-to-peak distance and peak height of irregularities and the frequency (number) of peaks can be adjusted (JP-A-2005-316450 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”)). However, this method is not sufficient in the effect of realizing dense black appearance or preventing reflection of outside light or external image, and improvements are demanded.
Furthermore, with the growing in size of the display, enhancement of display quality is recently demanded. The reflection on the outermost surface of a display is reduced with an attempt to realize denser black appearance or more successfully prevent the reflection of outside light or exterior image. However, the reduction in reflection makes it difficult to realize a homogeneous surface state (for example, no unevenness and no point defect). More specifically, the visibility of surface state is increased due to reduction in reflection and this requires higher coating precision and leads to difficulty in obtaining a homogeneous surface state. The visibility means that those less visible by virtue of high reflectance when the reflectance is high are clearly viewed as a result of reduction in the reflectance.
JP-A-2005-316450 discloses a technique of forming surface irregularities (irregularities having a large curvature; irregularities mainly affecting the reflecting property) by spherical particles, where irregularities having smooth undulation are formed, whereby reflection of outside light or exterior image is reduced and reduction in the refractive index becomes difficult.